1,3-Butylene glycol is a viscous, colorless, transparent, odorless liquid having a boiling point of 208° C., exhibits high solubility, and produces derivatives having excellent chemical stability.
1,3-Butylene glycol is used as a raw material of various synthetic resins and surfactants. In addition, since 1,3-butylene glycol has excellent hygroscopicity, low volatility, and low toxicity, it is also used as a material for cosmetics, hygroscopic agents, high-boiling-point solvents, and antifreezes. Particularly, in recent years, there has been increasing a demand for a non-toxic, non-irritant 1,3-butylene glycol in the cosmetic industry, since the butylene glycol has excellent properties as a humectant. Thus, an odorless butylene glycol is useful as a material of cosmetic grade.
However, when stored in a tank, 1,3-butylene glycol produced through a conventional process deteriorates with passage of time and issues a slight odor, and thus, long-term storage of the butylene glycol has been difficult.
Therefore, there has been a demand for providing an odorless 1,3-butylene glycol and which does not issue even a slight odor after storage for a long period of time.
Conventionally, the following three production processes for 1,3-butylene glycol have been known: (I) a process for producing 1,3-butylene glycol in which acetaldehyde is subjected to aldol condensation to thereby yield acetaldols, followed by catalytic reduction of the acetaldols (UK Patent No. 853266); (II) a process for producing 1,3-butylene glycol through a hydration reaction of 1,3-butylene oxide; and (III) a process for producing 1,3-butylene glycol from propylene and formaldehyde through the Prins reaction.
However, the process (II) is not practical, since an industrial production process therefor has not yet been established. Also, the process (III) is not practical because of a low yield.
Industrially, 1,3-butylene glycol is produced through the process (I). However, since acetaldols are a structurally unstable substance, and produces crotonaldehyde through dehydration, a variety of impurities such as butanol and 2-butanone are by-produced during a hydrogenation step (hereinafter, abbreviated as hydrogenation). Furthermore, in a step for recovering and recycling acetaldehyde, acetaldols are reacted with, for example, acetaldehyde, to thereby produce a variety of impurities. Separation of such impurities is difficult during a step for purifying 1,3-butylene glycol through, for example, distillation, and the impurities adversely affect the quality, particularly odor, of a product, for example, a product for cosmetics in particular.
Japanese Patent Application Laid-Open (kokai) No. 62-212384 discloses a process for producing substantially paraldol (trivial name of 2-(2-hydroxypropyl)-4-methyl-1,3-dioxane-6-ol), in which acetaldehyde is subjected to aldol condensation in the presence of an alkali catalyst, to thereby yield a crude reaction mixture containing aldoxane (trivial name of 2,4-dimethyl-1,3-dioxane-6-ol), and the aldoxane is thermally decomposed while acetaldehyde is obtained as a distillate.
Japanese Patent Application Laid-Open (kokai) No. 62-246529 discloses a process for producing 1,3-butylene glycol, in which a starting material containing paraldol as a substantially effective component is subjected to catalytic reduction.
Japanese Patent Publication (kokoku) No. 44-14328 discloses a process for producing crotonaldehyde, in which acetaldehyde is subjected to aldol condensation in the presence of an alkali catalyst, to thereby synthesize aldol, and dehydration of the aldol is carried out under heating in the presence of an acidic phosphoric acid ester.
Japanese Patent Application Laid-Open (kokai) No. 61-65834 discloses a process for purifying 1,3-butylene glycol, in which 1,3-butylene glycol having a purity of 98% or more is continuously distilled and purified under reduced pressure by use of a thin-film evaporator, while water is added to the butylene glycol.
Japanese Patent Application Laid-Open (kokai) No. 63-156738 discloses a process for distilling and purifying 1,3-butylene glycol, in which a hydrogenation reaction mixture of acetaldol is promptly subjected to flash evaporation under reduced pressure in advance, and the hydrogenation reaction mixture is subjected to distillation for removing high-boiling-point substances, and then to distillation for removing low-boiling-point substances, to thereby produce 1,3-butylene glycol as a bottom product.
Japanese Patent Application Laid-Open (kokai) No. 6-329664 discloses a process for producing a crude reaction mixture predominantly containing aldoxane and paraldol, in which, when acetaldehyde is subjected to aldol condensation in the presence of an alkali catalyst to thereby produce a crude reaction mixture predominantly containing aldoxane, acetaldehyde, water, and a small amount of crotonaldehyde, and then the aldoxane is thermally decomposed to thereby produce a crude reaction mixture predominantly containing the aldoxane and paraldol, acetaldehyde obtained as a distillate from the top of a thermal decomposition tower during thermal decomposition of the aldoxane is purified by use of a distillation tower including a side cut line having a decanter, and acetaldehyde substantially not containing crotonaldehyde is recycled in the aldol condensation step; and a process for producing 1,3-butylene glycol from the crude reaction mixture.
Japanese Patent Application Laid-Open (kokai) No. 7-258129 discloses a process for distilling and purifying 1,3-butylene glycol from a reaction mixture obtained through liquid-phase hydrogen reduction of acetaldol, in which, when 1,3-butylene glycol is subjected to distillation for removing high-boiling-point substances, at least one compound selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium borohydride, and potassium borohydride is added to the reaction mixture.
U.S. Pat. No. 3,489,655 discloses a process for improving the odor of 1,3-butylene glycol through a specific distillation process, in which heated 1,3-butylene glycol is brought into contact with only a non-catalytic material; specifically, stainless steel or glass.
However, the thus-produced odorless 1,3-butylene glycol involves a problem in that the butylene glycol deteriorates with passage of time and issues a slight odor when stored for a long period of time. Since a solution fed into a tower for removing high-boiling-point substances contains large amounts of high-boiling-point substances, through addition of an alkali metal, although the amount of low-boiling-point substances which are responsible for odor is reduced, simultaneously the high-boiling-point substances are decomposed to thereby yield low-boiling-point substances. It is to be noted that substances causing odor can be consequently reduced but only to a certain limited amount, and thus the butylene glycol deteriorates as time elapses, to thereby issue a slight odor when stored for a long period of time.
As described above, the conventional techniques are unsatisfactory for producing, at high yield and low cost, 1,3-butylene glycol which issues a considerably reduced odor after being stored for a long period of time, or 1,3-butylene glycol of high purity.
Meanwhile, butyl acetate is widely used as, for example, a solvent. Known production processes for butyl acetate include a process for distilling and purifying butyl acetate obtained through esterification of acetic acid and butanol in the presence of an acid catalyst.
Known production processes for butanol serving as a raw material include (i) the Hoechst-Wacker process, in which acetaldol is synthesized through dimerization of acetaldehyde and subjected to dehydration, to thereby yield crotonaldehyde, and then the crotonaldehyde is hydrogenated (hereinafter, occasionally also referred to hydrogenation); and (ii) the Reppe process, in which propylene, carbon monoxide, and water are reacted with one another in the presence of a catalyst.
On the other hand, when acetaldols are synthesized through condensation of acetaldehyde, and the acetaldols are hydrogenated, to thereby produce 1,3-butylene glycol, crotonaldehyde is by-produced during the synthesis step of the acetaldols. Therefore, there has been studied a process for producing butyl acetate from butanol which is by-produced through hydrogenation of the by-produced crotonaldehyde.
However, through the aforementioned techniques, production of butanol, or butyl acetate, having a quality comparable with that of a commercially available product is difficult, since the chameleon test value or the sulfuric acid coloring test value of butanol is low due to impurities contained in by-produced butanol.
Accordingly, the first invention group provides 1,3-butylene glycol of high purity which, at a period of three months after production, issues a considerably reduced odor, and which undergoes minimal change in quality with passage of time. The second invention group provides a process for producing, reliably and at high production efficiency, 1,3-butylene glycol which does not issue any problematic odor immediately after production and after three months of storage. The third invention group provides a process for producing 1,3-butylene glycol at high yield, in which corrosion of an apparatus employed in a hydrogenation step is minimized. The fourth invention group provides a high-yield, economical purification process for providing 1,3-butylene glycol of high purity. Further, the fifth invention group provides a high-yield, economical process for producing purified 1,3-butylene glycol which issues no odor or issues only a considerably reduced odor.
Furthermore, the sixth invention group provides a process for producing, as a by-product, butanol containing small amounts of impurities, in which, when acetaldol is hydrogenated to thereby produce 1,3-butylene glycol, crotonaldehyde which is by-produced during synthesis of the acetaldols is simultaneously hydrogenated, to thereby allow butanol to be by-produced, and the by-produced butanol is purified; and a process for producing butyl acetate of high quality from the thus-obtained butanol.